Why do we boil the wort? I am putting on a Winter W.kit that calls for boiling only a third of the syrup for an hour the other thirds for 15 & 10 each . What does the boiling do that is apparently not wanted for this recipe?

You're using a technique called "late addition" that helps to keep the color lighter and increases hop utilization with the lower-gravity wort thoughout most of the boil. We boil wort to extract hop goodness and to coagulate proteins and develop flavors as well as to increase efficiency in the all-grain process (by allowing for more sugar extraction for the grain). But you can make good beer with a much shorter boil, too, just have to adjust the recipe.

I agree with shadetree in regard to those specific instructions. I would think another reason to boil wort would be to sanitize it....... Not saying you need a full hour to do that, but some level of heat for a certain amount of time is going to reduce the likelihood of bad things taking over your beer.

Thanks for the replies. My W.Warm. kit calls for adding 3lbs of syrup to 2.5 gal. water. I assume this gives the best gravity for hop extraction?(2 oz)Or is there something going on in the longer boil Since it calls for adding the rest (6lb) of the malt for the last 15 min can I assume 15 min is really long enough to boil the full wort. Or is there something going on in the longer boil? I'm just trying to understand why different recipes are different.

15 minutes is long enough to sanitize the wort, however it wouldn't belong enough to extract the hop bitterness. You can get pre hopped canned extract and do a short boil with it as the bittering hops are already in it.

Most recipes are similar in regards to boil times, just different hop and malt profiles.

it calls for adding the first 2oz of hops in the long boil of the first 3 lb of malt . So i guess thats the hop extraction . And simply bringing the wort to boil after adding the next six lbs would take care of sanitation. Is there something else going on?

Heat (i.e., boiling) is necessary to induce a change (isomerization) in the molecule ("alpha acid") found in Hops that's associated with the bittering flavor in beer. Without the isomerization, alpha acids are insoluble. Therefore, if you want to add the hop flavor that is commonly associated with beer, you need to boil your wort + hops.

I haven't explored the literature fully on this, but I speculate that boil length is proportional to the percent of alpha acids isomerized, and therefore correlates with the end-result beer bitterness. You could theoretically achieve the same dissolution of bittering compounds in a shorter boil using a greater quantity of hops (and this is done; see "hopbursting"), but I also speculate that the desire to keep costs low and limit suspended solids promotes the use of the 60-minute boil.

Longer boils also change the nature of the sugars in the wort (i.e., carmelization) and can promote different, more complex flavor profiles, as well as darker colors.

Silentknyght wrote:Heat (i.e., boiling) is necessary to induce a change (isomerization) in the molecule ("alpha acid") found in Hops that's associated with the bittering flavor in beer. Without the isomerization, alpha acids are insoluble. Therefore, if you want to add the hop flavor that is commonly associated with beer, you need to boil your wort + hops.

I haven't explored the literature fully on this, but I speculate that boil length is proportional to the percent of alpha acids isomerized, and therefore correlates with the end-result beer bitterness. You could theoretically achieve the same dissolution of bittering compounds in a shorter boil using a greater quantity of hops (and this is done; see "hopbursting"), but I also speculate that the desire to keep costs low and limit suspended solids promotes the use of the 60-minute boil.

Longer boils also change the nature of the sugars in the wort (i.e., carmelization) and can promote different, more complex flavor profiles, as well as darker colors.

To get the hop bitterness you associate with beer, you MUST boil them for 60 minutes. There is no amount of hops you can add later in the boil that will achieve the same thing as a 60 minute addition does.

As the acids are isomerized, you get different character from the hops. At 60 minutes, it's all bitterness; no flavor, no aroma, only bitterness. The later the addition the more the hop character goes from bitterness, to flavor, to aroma. A dry hop adds only aroma.

So if you are looking for a little bitterness and some hop flavor with a great hop aroma, you could essentially have a 30 minute boil with an oz (or 2) of hops, then dry hop it. Normally the reason for a 60 minute boil is to get the traditional hop bitterness we all know and love.

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Silentknyght wrote:I haven't explored the literature fully on this, but I speculate that boil length is proportional to the percent of alpha acids isomerized, and therefore correlates with the end-result beer bitterness.

There's a useful table in How to Brew that lays it all out for boil gravities up to 1.120 and times up to 2 hours. There's a pretty steep diminishing returns thing going on.

For a 2 hour boil with a gravity of 1.050, 70% of the total hop utilization comes from the first 30 minutes, 24% during the next 30 minutes, and only 6% is attributable to the second hour.

Silentknyght wrote:I haven't explored the literature fully on this, but I speculate that boil length is proportional to the percent of alpha acids isomerized, and therefore correlates with the end-result beer bitterness.

There's a useful table in How to Brew that lays it all out for boil gravities up to 1.120 and times up to 2 hours. There's a pretty steep diminishing returns thing going on.

For a 2 hour boil with a gravity of 1.050, 70% of the total hop utilization comes from the first 30 minutes, 24% during the next 30 minutes, and only 6% is attributable to the second hour.

Ahh, word choice error! I should have said "correlates," not proportional; I meant "correlates" in my head. I would expect diminishing returns, of course, on a logarithmic-type graph.